Neuromuscul Disord 2017 Sep 3;27(9):852-855. Epub 2017 May 3.

MRC Centre for Neuromuscular Diseases and Department of Molecular Neuroscience, University College London Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK; Dubowitz Neuromuscular Centre, Great Ormond Street Hospital, London WC1N 3JH, UK.

Diagnosis of McArdle disease is frequently delayed by many years following the first presentation of symptoms to a health professional. The aim of this study was to investigate the importance of misdiagnosis in delaying diagnosis of McArdle disease. The frequency of misdiagnosis, duration of diagnostic delay, categories of misdiagnoses and inappropriate medical interventions were assessed in 50 genetically confirmed patients. Read More

Am J Case Rep 2016 Nov 30;17:905-908. Epub 2016 Nov 30.

MRC Centre for Neuromuscular Diseases and Division of Neuropathology, University College London Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, United Kingdom.

BACKGROUND McArdle disease is a glycogen storage disorder mainly characterized by exercise intolerance. Prolonged muscle contracture is also a feature of this condition and may lead to rhabdomyolysis (RM), which is a serious event characterized by acute skeletal muscle damage.  CASE REPORT A 44-year-old female patient presented with an acute contracture of the posterior neck muscles, causing severe nuchal rigidity. Read More

Muscle Nerve 2017 Jun 16;55(6):916-918. Epub 2016 Dec 16.

Division of Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, PO Box 115, Newlands, 7725, South Africa.

Introduction: McArdle disease is a metabolic myopathy that presents with exercise intolerance and episodic rhabdomyolysis. Excessive muscle recruitment has also been shown to be present during strenuous exercise, suggesting decreased power output. These findings could potentially be explained by either impaired contractility, decreased fiber size, or altered fiber type proportion. Read More

Genet Med 2016 Nov 25;18(11):1128-1135. Epub 2016 Feb 25.

Laboratorio de Enfermedades Mitocondriales y Neuromusculares, Hospital 12 de Octubre, Madrid, Spain.

Purpose: McArdle disease is a metabolic disorder caused by pathogenic mutations in the PYGM gene. Timely diagnosis can sometimes be difficult with direct genomic analysis, which requires additional studies of cDNA from muscle transcripts. Although the "nonsense-mediated mRNA decay" (NMD) eliminates tissue-specific aberrant transcripts, there is some residual transcription of tissue-specific genes in virtually all cells, such as peripheral blood mononuclear cells (PBMCs). Read More

Neurol Res 2016 Dec 20;38(12):1052-1055. Epub 2016 Oct 20.

a Department of Neurology , Martin-Luther-University Halle-Wittenberg , Halle (Saale) , Germany.

During physical activity in McArdle patients, little or no lactate is released in the skeletal muscle. However, excessive ammonia production has frequently been reported in these patients. Production of ammonia is catalysed by AMP deaminase (AMPD) and adenylate kinase (AK). Read More

J Clin Psychopharmacol 2016 Aug;36(4):406-8

Department of Nephrology-Transplantation University Hospital Dijon, France Association Néphrologie-Dialyse-Transplantation Dijon, France Department of Nephrology-Transplantation University Hospital Dijon, France

Am J Physiol Regul Integr Comp Physiol 2016 Aug 8;311(2):R307-14. Epub 2016 Jun 8.

Copenhagen Neuromuscular Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark;

McArdle disease (muscle glycogenosis type V) is a disease caused by myophosphorylase deficiency leading to "blocked" glycogen breakdown. A significant but varying glycogen accumulation in especially distal hind limb muscles of mice affected by McArdle disease has recently been demonstrated. In this study, we investigated how myophosphorylase deficiency affects glucose metabolism in hind limb muscle of 20-wk-old McArdle mice and vastus lateralis muscles from patients with McArdle disease. Read More

J Clin Neurol 2016 Jul 3;12(3):373-5. Epub 2016 Jun 3.

Department of Neurology, Mokdong Hospital, Ewha Womans University School of Medicine, Seoul, Korea.

Acta Myol 2015 Dec;34(2-3):120-125

Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.

McArdle's disease is the most common metabolic myopathy of muscle carbohydrate metabolism, due to deficiency of myophosphorylase and alteration of glycogen breakdown in muscle. The clinical manifestations usually begin in young adulthood, with exercise intolerance, exercise-induced muscle cramps, pain and recurrent episodes of myoglobinuria. Many patients experience the second wind phenomenon, characterized by an improved tolerance for aerobic exercise approximately after eight minutes of motor activity, secondary to the increased availability of blood glucose and free fatty acids associated to an enhanced glucose uptake by muscle cells. Read More

J Neuropathol Exp Neurol 2016 May 30;75(5):441-54. Epub 2016 Mar 30.

From the Copenhagen Neuromuscular Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (TOK, TLN, JV); and Mitochondrial Pathology and Neuromuscular Disorders Laboratory, Vall d'Hebron Research Institute, Barcelona, Spain and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain (TP, AB, ALA).

McArdle disease (muscle glycogenosis type V) is caused by myophosphorylase deficiency, which leads to impaired glycogen breakdown. We investigated how myophosphorylase deficiency affects muscle physiology, morphology, and glucose metabolism in 20-week-old McArdle mice and compared the findings to those in McArdle disease patients. Muscle contractions in the McArdle mice were affected by structural degeneration due to glycogen accumulation, and glycolytic muscles fatigued prematurely, as occurs in the muscles of McArdle disease patients. Read More

Masui 2015 Nov;64(11):1203-5

McArdle disease, known as type V glycogen storage disease, is a rare skeletal muscle disorder. Patients with McArdle disease lack skeletal muscle specific glycogen phosphorylase, and myophosphorylase. This subsequently leads to an elevation in serum creatine kinase levels, and results in suffering from exercise intolerance. Read More

J Hand Surg Am 2015 Dec;40(12):2377-9

Division of Plastic and Reconstructive Surgery, Department of Surgery, Washington University School of Medicine, Saint Louis, MO.

Glycogen storage disorders are rare diseases of metabolism that are usually diagnosed when a patient presents with recurrent fatigue, muscle pains, and exercise intolerance. In this case report, we describe a patient who presented with the second episode of nontraumatic compartment syndrome over a 10-year span. Because of the obscure presentation, we performed a muscle biopsy, which on muscle phosphorylase staining revealed McArdle disease (glycogen storage disease type V). Read More

Med Sci Sports Exerc 2016 Apr;48(4):673-9

1Translational Research Laboratoy in Neuromuscular Diseases, Neurosciences Department, Germans Trias i Pujol Research Institute and Campus Can Ruti, Autonomous University of Barcelona, Badalona, SPAIN; 2Sports Sciences and Computing Department, Pablo de Olavide University, Sevilla, SPAIN; 312 de Octubre Hospital Research Institute (i + 12), Madrid, SPAIN; 4Mitochondrial and Neuromuscular Diseases Laboratory, 12 de Octubre Hospital, Madrid, SPAIN; 5Centre for Biomedical Network Research on Rare Diseases (CIBERER), Carlos III Health Institute, Madrid, SPAIN; 6Centre for Sports Medicine and Human Performance, Brunel University, London, UNITED KINGDOM; 7Neuromuscular and Mitochondrial Pathology Department, Vall d'Hebron University Hospital, Research Institute (VHIR), Autonomous University of Barcelona, Barcelona, SPAIN; 8Rare Diseases Unit, Pediatric Service, Germans Trias i Pujol University Hospital, Badalona, Barcelona, SPAIN; 9Neuromuscular Unit Neurology Service, Germans Trias i Pujol University Hospital, Badalona, Barcelona, SPAIN; and 10School of Research and Doctorate Studies, European University, Madrid, SPAIN.

McArdle disease is due to an inborn defect in the muscle isoform of glycogen phosphorylase (or "myophosphorylase"), the enzyme that catalyzes the first step of glycogenolysis. This condition is still not fully understood, and although advances in research would help patients immeasurably, these would also enhance our understanding of exercise metabolism. It has been 10 yr since the first published report demonstrating the benefits of regular aerobic exercise for these patients. Read More

Physiol Genomics 2016 Feb 13;48(2):93-100. Epub 2015 Oct 13.

Instituto de Investigación Hospital 12 de Octubre (i+12), Madrid, Spain; and Universidad Europea, Madrid, Spain.

McArdle disease (glycogen storage disease type V) is caused by inherited deficiency of a key enzyme in muscle metabolism, the skeletal muscle-specific isoform of glycogen phosphorylase, "myophosphorylase," which is encoded by the PYGM gene. Here we review the main pathophysiological, genotypic, and phenotypic features of McArdle disease and their interactions. To date, moderate-intensity exercise (together with pre-exercise carbohydrate ingestion) is the only treatment option that has proven useful for these patients. Read More

Physiol Genomics 2016 Feb 22;48(2):82-92. Epub 2015 Sep 22.

Department of Neurosciences, Institut d'Investigació en Ciències de la Salut Germans Trias i Pujol i Campus Can Ruti, Universitat Autònoma de Barcelona, Badalona, Spain; and Instituto de Investigación Hospital 12 de Octubre (i+12) and Universidad Europea, Madrid, Spain.

The extremes of exercise capacity and health are considered a complex interplay between genes and the environment. In general, the study of animal models has proven critical for deep mechanistic exploration that provides guidance for focused and hypothesis-driven discovery in humans. Hypotheses underlying molecular mechanisms of disease and gene/tissue function can be tested in rodents to generate sufficient evidence to resolve and progress our understanding of human biology. Read More

No To Hattatsu 2015 Mar;47(2):94-8

Curr Rheumatol Rep 2015 Oct;17(10):63

Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Patients with autoimmune myositis typically present with muscle weakness, elevated serum levels of muscle enzymes, and abnormal muscle biopsies. However, patients with other acquired myopathies or genetic muscle diseases may have remarkably similar presentations. Making the correct diagnosis of another muscle disease can prevent these patients from being exposed to the risks of immunosuppressive medications, which benefit those with myositis, but not those with other types of muscle disease. Read More

Genet Med 2015 Aug;17(8):680-1

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Betheseda, Maryland, USA.

Genet Med 2015 Aug;17(8):679-80

1] Instituto de Investigación Hospital 12 de Octubre (i+12), Madrid, Spain [2] Universidad Europea, Madrid, Spain.

Reumatol Clin 2016 May-Jun;12(3):161-3. Epub 2015 Jul 30.

Servicio de Anatomía Patológica, Hospital Meixoeiro, Vigo, España.

A high serum level of creatine kinase (CK) is a common reason for referring to medical specialities. Myopathies are one of the causes of elevated levels of CK. McArdle disease is the most common disorder of skeletal muscle carbohydrate metabolism. Read More

Muscle Nerve 2015 Dec 24;52(6):1136-7. Epub 2015 Sep 24.

Department of Neurosciences, Institut d'Investigació en Ciències de la Salut Germans Trias i Pujol I Campus Can Ruti, Universitat Autònoma de Barcelona, Badalona, Spain.

Neuromuscul Disord 2015 Sep 27;25(9):739-45. Epub 2015 May 27.

Vall D'Hebron Research Institute and Centre for Biomedical Network Research on Rare Diseases (CIBERER), Barcelona, Catalonia, Spain.

Muscle Nerve 2015 Nov 30;52(5):891-5. Epub 2015 Jun 30.

Neurology Clinics A & C, The Cyprus Institute of Neurology and Genetics, P.O. Box 23462, 1683, Nicosia, Cyprus.

Introduction: We report the clinical, biochemical, and molecular findings in a Cypriot family with minimally symptomatic McArdle disease.

Methods: Myophosphorylase in muscle was assessed by histochemistry, quantitative spectrophotometry, and western blot analysis. Mutation identification was performed by PCR amplification of all PYGM exons, followed by bidirectional sequencing. Read More

J Clin Endocrinol Metab 2015 Aug 1;100(8):E1096-104. Epub 2015 Jun 1.

Neuromuscular Research Unit, Department of Neurology (M.C.O., T.D.J., S.H., N.P., J.V.), Copenhagen Muscle Research Center (M.C.O., T.D.J., S.H., N.P., J.V., G.H.), and Clinical Metabolomics Core Facility (G.H.), Rigshospitalet, DK-2100 Copenhagen, Denmark; Department of Biomedical Sciences (G.H.), Faculty of Health and Medical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark; Neuromuscular Center (T.T., K.H., R.G.H.), Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, and the Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas 75235; and Department of Neurology (R.G.H.), North Texas VA Medical Center, Dallas, Texas 75216.

Context: Patients with blocked muscle glycogen breakdown (McArdle disease) have severely reduced exercise capacity compared to healthy individuals and are not assumed to produce lactate during exercise.

Objectives: The objectives were: 1) to quantify systemic and muscle lactate kinetics and oxidation rates and muscle energy utilization during exercise in patients with McArdle disease; and 2) to elucidate the role of lactate formation in muscle energy production.

Design And Setting: This was a single trial in a hospital. Read More

Neurol Sci 2015 Sep 19;36(9):1721-3. Epub 2015 May 19.

Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari, Bari, Italy,

Hum Mutat 2015 Jul 3;36(7):669-78. Epub 2015 Jun 3.

Departament de Patologia Mitocondrial i Neuromuscular, Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), , Universitat Autónoma de Barcelona, Barcelona, Spain.

McArdle disease is an autosomal-recessive disorder caused by inherited deficiency of the muscle isoform of glycogen phosphorylase (or "myophosphorylase"), which catalyzes the first step of glycogen catabolism, releasing glucose-1-phosphate from glycogen deposits. As a result, muscle metabolism is impaired, leading to different degrees of exercise intolerance. Patients range from asymptomatic to severely affected, including in some cases, limitations in activities of daily living. Read More

J Clin Pathol 2015 Jun 15;68(6):410-7. Epub 2015 Apr 15.

Queen Square Centre for Neuromuscular Diseases, London, UK.

Metabolic myopathies (MM) are rare inherited primary muscle disorders that are mainly due to abnormalities of muscle energy metabolism resulting in skeletal muscle dysfunction. These diseases include disorders of fatty acid oxidation, glyco(geno)lytic muscle disorders and mitochondrial respiratory chain (MRC) disease. Clinically these disorders present with a range of symptoms including infantile hypotonia, myalgia/exercise tolerance, chronic or acute muscle weakness, cramps/spasms/stiffness or episodic acute rhabdomyolysis. Read More

J Physiol 2015 Jun 18;593(12):2693-706. Epub 2015 May 18.

Neuromuscular and Mitochondrial Disorders Laboratory, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.

Key Points: This is the first study to analyse the effect of muscle glycogen phosphorylase depletion in metabolically different muscle types. In McArdle mice, muscle glycogen phosphorylase is absent in both oxidative and glycolytic muscles. In McArdle mice, the glycogen debranching enzyme (catabolic) is increased in oxidative muscles, whereas the glycogen branching enzyme (anabolic) is increased in glycolytic muscles. Read More

Dis Model Mech 2015 May 11;8(5):467-72. Epub 2015 Mar 11.

Mitochondrial Pathology and Neuromuscular Disorders Laboratory, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona 08035, Spain Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid 28029, Spain

McArdle disease, also termed 'glycogen storage disease type V', is a disorder of skeletal muscle carbohydrate metabolism caused by inherited deficiency of the muscle-specific isoform of glycogen phosphorylase (GP-MM). It is an autosomic recessive disorder that is caused by mutations in the PYGM gene and typically presents with exercise intolerance, i.e. Read More

Genet Med 2015 Dec 5;17(12):1002-6. Epub 2015 Mar 5.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA.

Purpose: McArdle disease is one of the most common glycogen storage disorders. Although the exact prevalence is not known, it has been estimated to be 1 in 100,000 patients in the United States. More than 100 mutations in PYGM have been associated with this disorder. Read More

Eur J Neurol 2015 Jun 5;22(6):933-40. Epub 2015 Mar 5.

Institute of Myology, Pitié-Salpêtrière Hospital, Paris, France.

Background And Purpose: This was a retrospective study to assess the diagnostic value of the non-ischaemic forearm exercise test in detecting McArdle's disease.

Methods: The study is a retrospective diagnostic study over 15 years (1999-2013) on a referred sample of patients suffering from exercise intolerance and various muscle complaints, generally with elevated creatine kinase (CK). In all, 1226 patients underwent the non-ischaemic forearm exercise test. Read More

Dtsch Med Wochenschr 2015 Feb 6;140(3):202-5. Epub 2015 Feb 6.

Klinik und Poliklinik für Neurologie, Universitätsklinik Köln.

Unlabelled: HISTORY AND PRESENTATION AT ADMISSION: A 25-year-old male patient presented with acute left sided chest pain. The patient reported no physical exercise but daytime fasting (with neither food nor liquid intake) which he had started several days before.

Investigations: ECG, echocardiography and chest X-ray were normal, but blood examination revealed elevated levels for creatine kinase (CK) and lactate dehydrogenase (LDH). Read More

Neuromuscul Disord 2015 Feb 13;25(2):111-9. Epub 2014 Oct 13.

Robert Jones and Agnes Hunt Orthopaedic hospital, Oswestry, United Kingdom.

McArdle disease is due to an absence of the enzyme muscle glycogen phosphorylase and results in significant physical impairment in humans. We hypothesised that sodium valproate, an HDAC inhibitor, might have the ability to up-regulate the enzyme. We treated McArdle sheep with sodium valproate given enterically at 20-60 mg/kg body wt. Read More

Cochrane Database Syst Rev 2014 Nov 12(11):CD003458. Epub 2014 Nov 12.

Background McArdle disease (Glycogen Storage Disease type V) is caused by an absence of muscle phosphorylase leading to exercise intolerance,myoglobinuria rhabdomyolysis and acute renal failure. This is an update of a review first published in 2004.Objectives To review systematically the evidence from randomised controlled trials (RCTs) of pharmacological or nutritional treatments for improving exercise performance and quality of life in McArdle disease. Read More

BMJ Case Rep 2014 Oct 7;2014. Epub 2014 Oct 7.

MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK.

Despite the majority of patients with McArdle disease reporting symptoms including fatigue, cramps and episodes of myoglobinuria from early childhood, diagnosis is often delayed by several decades. Additionally, many individuals with rhabdomyolysis remain undiagnosed. The occurrence of symptoms during exercise, particularly isometric muscle contraction such as heavy lifting, is well known in McArdle disease. Read More

Ceylon Med J 2014 Sep;59(3):99-100

University Medical Unit, Teaching Hospital Karapitiya, Galle, Sri Lanka.

Neuromuscul Disord 2014 Dec 21;24(12):1079-86. Epub 2014 Aug 21.

Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain. Electronic address:

McArdle disease is caused by an inherited deficiency of the enzyme myophosphorylase, resulting in exercise intolerance from childhood and acute crises of early fatigue and contractures. In severe cases, these manifestations can be accompanied by rhabdomyolysis, myoglobinuria, and fatal renal failure. Diagnosis of McArdle disease is based on clinical diagnostic tests, together with an absence of myophosphorylase activity in skeletal muscle biopsies and genetic analysis of the myophosphorylase-encoding gene, PYGM. Read More

Med Sci Sports Exerc 2015 Apr;47(4):799-808

1Department of Sport and Informatics, Section of Physical Education and Sports, Faculty of Sport, Universidad Pablo de Olavide, Sevilla, SPAIN; and 2European University and Research Institute Hospital 12 de Octubre, Madrid, SPAIN.

Background: This study sought to determine whether health-related quality of life (HRQoL) could be related to cardiorespiratory fitness (CRF) and/or physical activity (PA) in patients with McArdle disease and to compare the CRF and HRQoL data obtained with normative data for age- and sex-matched healthy subjects.

Methods: Eighty-one adult patients with McArdle disease underwent aerobic capacity testing to determine peak oxygen uptake (V˙O2peak), among other variables. HRQoL (Short Form 36-Item Health Survey questionnaire version 2 (SF-36 version 2)) and PA (International Physical Activity Questionnaire) questionnaires were completed by 45 of the patients. Read More

Arq Neuropsiquiatr 2014 Jul;72(7):538-41

MRC Centre for Neuromuscular Diseases and Division of Neuropathology, University College London Institute of Neurology, Queen Square, London, United Kingdom.

McArdle disease is the most common of the glycogen storage diseases. Onset of symptoms is usually in childhood with muscle pain and restricted exercise capacity. Signs and symptoms are often ignored in children or put down to 'growing pains' and thus diagnosis is often delayed. Read More

J Inherit Metab Dis 2015 Mar 23;38(2):221-30. Epub 2014 Jul 23.

Neuromuscular Diseases Unit, Institut de Recerca del Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Av. Maria Claret 167, 08025, Barcelona, Spain,

Numerous biomedical advances have been made since Carl and Gerty Cori discovered the enzyme phosphorylase in the 1940s and the Scottish physician Brian McArdle reported in 1951 a previously 'undescribed disorder characterized by a gross failure of the breakdown in muscle of glycogen'. Today we know that this disorder, commonly known as 'McArdle disease', is caused by inherited deficiency of the muscle isoform of glycogen phosphorylase (GP). Here we review the main aspects of the 'pathogenomics' of this disease including, among others: the spectrum of mutations in the gene (PYGM) encoding muscle GP; the interplay between the different tissue GP isoforms in cellular cultures and in patients; what can we learn from naturally occurring and recently laboratory-generated animal models of the disease; and potential therapies. Read More

J Korean Med Sci 2014 Jul 11;29(7):1021-4. Epub 2014 Jul 11.

Department of Neurology, Yonsei University College of Medicine, Seoul, Korea. ; Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul, Korea.

Glycogen storage disease type V (GSD-V) is the most common disorder of muscle glycogenosis with characteristic clinical and laboratory findings. A 32-yr-old woman complained of exercise intolerance and myoglobulinuria since early adolescence. She reported several episodes of second-wind phenomenon. Read More

Rev Esp Anestesiol Reanim 2015 Feb 14;62(2):101-3. Epub 2014 Jul 14.

Servicio de Anestesiología, Reanimación y Terapéutica del dolor, Hospital San Pedro de Logroño, Logroño, España.

McArdle disease is a metabolic myopathy that can may lead to severe perioperative problems. A case is reported of a woman with a history of McArdle disease, who was scheduled for a mastectomy. An understanding of the physiology and pathology, and the application of appropriate preventive measures can avoid complications. Read More

Sports Med 2014 Nov;44(11):1531-44

Universidad Pablo Olavide, Sevilla, Spain.

McArdle disease is arguably the paradigm of exercise intolerance in humans. This disorder is caused by inherited deficiency of myophosphorylase, the enzyme isoform that initiates glycogen breakdown in skeletal muscles. Because patients are unable to obtain energy from their muscle glycogen stores, this disease provides an interesting model of study for exercise physiologists, allowing insight to be gained into the understanding of glycogen-dependent muscle functions. Read More

Biology (Basel) 2014 Feb 25;3(1):157-66. Epub 2014 Feb 25.

Department of Sports Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.

McArdle disease (glycogen storage disease Type V; MD) is a metabolic myopathy caused by a deficiency in muscle glycogen phosphorylase. Since muscle glycogen is an important fuel for muscle during exercise, this inborn error of metabolism provides a model for understanding the role of glycogen in muscle function and the compensatory adaptations that occur in response to impaired glycogenolysis. Patients with MD have exercise intolerance with symptoms including premature fatigue, myalgia, and/or muscle cramps. Read More

J Sports Sci 2014 14;32(16):1561-9. Epub 2014 Apr 14.

a Department of Clinical Sciences and Nutrition , University of Chester , Chester , UK.

The aim of this study was to assess a 12-min self-paced walking test in patients with McArdle disease. Twenty patients (44.7 ± 11 years; 11 female) performed the walking test where walking speed, distance walked, heart rate (HR) and perceived muscle pain (Borg CR10 scale) were measured. Read More

J Appl Physiol (1985) 2014 May 20;116(9):1230-7. Epub 2014 Mar 20.

Institute of Bioimaging and Molecular Physiology, National Research Council, Segrate, Italy;

Patients with McArdle's disease (McA) typically show the "second-wind" phenomenon, a sudden decrease in heart rate (HR) and an improved exercise tolerance occurring after a few minutes of exercise. In the present study, we investigated whether in McA a first bout of exercise determines a second wind during a second bout, separated by the first by a few minutes of recovery. Eight McA (44 ± 4 yr) and a control group of six mitochondrial myopathy patients (51 ± 6 yr) performed two repetitions (CWR1 and CWR2) of 6-min constant work rate exercise (∼50% of peak work rate) separated by 6-min (SHORT) or 18-min (LONG) recovery. Read More

Endocrine 2014 Sep 4;47(1):340-1. Epub 2014 Feb 4.

Largo Professor Abel Salazar, Hospital de Santo António, Edifício Neoclássico, 4099-001, Porto, Portugal,

Neuromuscul Disord 2014 Feb 26;24(2):167-77. Epub 2013 Oct 26.

Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.

McArdle disease is caused by a deficiency of myophosphorylase and currently a satisfactory treatment is not available. The injection of notexin into, or the layering of notexin onto, the muscles of affected sheep resulted in necrosis followed by regeneration of muscle fibres with the expression of both non-muscle isoforms of phosphorylase within the fibres and a reduction of the amount of glycogen in the muscle with an increase in the strength of contraction and a decrease in fatiguability in the muscle fibres. The sustained re-expression of both the brain and liver isoforms of phosphorylase within the muscle fibres provides further emphasis that strategies to enhance the re-expression of these isoforms should be investigated as a possible treatment for McArdle disease. Read More

Tenn Med 2013 Nov-Dec;106(10):33, 37

Chattanooga Emergency Medicine, TN, USA.

McArdle's Disease is a rare glycogen disease involving deficiency in muscle phosphorylase. This deficiency can lead to rhabdomyolysis and subsequently renal failure. McArdle's Disease has a similar presentation as several other metabolic myopathies with exercise-induced fatigue, myalgias, weakness or unexplained rhabdomyolysis. Read More